[PATCH 3.19 038/101] sunrpc: make debugfs file creation failure non-fatal

Greg Kroah-Hartman
2015-04-17T14:05:53Z

From: Jeff Layton <jlayton@poochiereds.net>

commit f9c72d10d6fbf949558cd088389a42213ed7b12d upstream.

We currently have a problem that SELinux policy is being enforced when
creating debugfs files. If a debugfs file is created as a side effect of
doing some syscall, then that creation can fail if the SELinux policy
for that process prevents it.

This seems wrong. We don't do that for files under /proc, for instance,
so Bruce has proposed a patch to fix that.

While discussing that patch however, Greg K.H. stated:

"No kernel code should care / fail if a debugfs function fails, so
please fix up the sunrpc code first."

This patch converts all of the sunrpc debugfs setup code to be void
return functins, and the callers to not look for errors from those
functions.

This should allow rpc_clnt and rpc_xprt creation to work, even if the
kernel fails to create debugfs files for some reason.

Symptoms were failing krb5 mounts on systems using gss-proxy and
selinux.

Fixes: 388f0c776781 "sunrpc: add a debugfs rpc_xprt directory..."
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/linux/sunrpc/debug.h | 18 +++++++-------
net/sunrpc/clnt.c | 4 ---
net/sunrpc/debugfs.c | 52 +++++++++++++++++++++++--------------------
net/sunrpc/sunrpc_syms.c | 7 -----
net/sunrpc/xprt.c | 7 -----
5 files changed, 41 insertions(+), 47 deletions(-)

--- a/include/linux/sunrpc/debug.h
+++ b/include/linux/sunrpc/debug.h
@@ -60,17 +60,17 @@ struct rpc_xprt;
#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
void rpc_register_sysctl(void);
void rpc_unregister_sysctl(void);
-int sunrpc_debugfs_init(void);
+void sunrpc_debugfs_init(void);
void sunrpc_debugfs_exit(void);
-int rpc_clnt_debugfs_register(struct rpc_clnt *);
+void rpc_clnt_debugfs_register(struct rpc_clnt *);
void rpc_clnt_debugfs_unregister(struct rpc_clnt *);
-int rpc_xprt_debugfs_register(struct rpc_xprt *);
+void rpc_xprt_debugfs_register(struct rpc_xprt *);
void rpc_xprt_debugfs_unregister(struct rpc_xprt *);
#else
-static inline int
+static inline void
sunrpc_debugfs_init(void)
{
- return 0;
+ return;
}

static inline void
@@ -79,10 +79,10 @@ sunrpc_debugfs_exit(void)
return;
}

-static inline int
+static inline void
rpc_clnt_debugfs_register(struct rpc_clnt *clnt)
{
- return 0;
+ return;
}

static inline void
@@ -91,10 +91,10 @@ rpc_clnt_debugfs_unregister(struct rpc_c
return;
}

-static inline int
+static inline void
rpc_xprt_debugfs_register(struct rpc_xprt *xprt)
{
- return 0;
+ return;
}

static inline void
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -303,9 +303,7 @@ static int rpc_client_register(struct rp
struct super_block *pipefs_sb;
int err;

- err = rpc_clnt_debugfs_register(clnt);
- if (err)
- return err;
+ rpc_clnt_debugfs_register(clnt);

pipefs_sb = rpc_get_sb_net(net);
if (pipefs_sb) {
--- a/net/sunrpc/debugfs.c
+++ b/net/sunrpc/debugfs.c
@@ -129,48 +129,52 @@ static const struct file_operations task
.release = tasks_release,
};

-int
+void
rpc_clnt_debugfs_register(struct rpc_clnt *clnt)
{
- int len, err;
+ int len;
char name[24]; /* enough for "../../rpc_xprt/ + 8 hex digits + NULL */
+ struct rpc_xprt *xprt;

/* Already registered? */
- if (clnt->cl_debugfs)
- return 0;
+ if (clnt->cl_debugfs || !rpc_clnt_dir)
+ return;

len = snprintf(name, sizeof(name), "%x", clnt->cl_clid);
if (len >= sizeof(name))
- return -EINVAL;
+ return;

/* make the per-client dir */
clnt->cl_debugfs = debugfs_create_dir(name, rpc_clnt_dir);
if (!clnt->cl_debugfs)
- return -ENOMEM;
+ return;

/* make tasks file */
- err = -ENOMEM;
if (!debugfs_create_file("tasks", S_IFREG | S_IRUSR, clnt->cl_debugfs,
clnt, &tasks_fops))
goto out_err;

- err = -EINVAL;
rcu_read_lock();
+ xprt = rcu_dereference(clnt->cl_xprt);
+ /* no "debugfs" dentry? Don't bother with the symlink. */
+ if (!xprt->debugfs) {
+ rcu_read_unlock();
+ return;
+ }
len = snprintf(name, sizeof(name), "../../rpc_xprt/%s",
- rcu_dereference(clnt->cl_xprt)->debugfs->d_name.name);
+ xprt->debugfs->d_name.name);
rcu_read_unlock();
+
if (len >= sizeof(name))
goto out_err;

- err = -ENOMEM;
if (!debugfs_create_symlink("xprt", clnt->cl_debugfs, name))
goto out_err;

- return 0;
+ return;
out_err:
debugfs_remove_recursive(clnt->cl_debugfs);
clnt->cl_debugfs = NULL;
- return err;
}

void
@@ -226,33 +230,33 @@ static const struct file_operations xprt
.release = xprt_info_release,
};

-int
+void
rpc_xprt_debugfs_register(struct rpc_xprt *xprt)
{
int len, id;
static atomic_t cur_id;
char name[9]; /* 8 hex digits + NULL term */

+ if (!rpc_xprt_dir)
+ return;
+
id = (unsigned int)atomic_inc_return(&cur_id);

len = snprintf(name, sizeof(name), "%x", id);
if (len >= sizeof(name))
- return -EINVAL;
+ return;

/* make the per-client dir */
xprt->debugfs = debugfs_create_dir(name, rpc_xprt_dir);
if (!xprt->debugfs)
- return -ENOMEM;
+ return;

/* make tasks file */
if (!debugfs_create_file("info", S_IFREG | S_IRUSR, xprt->debugfs,
xprt, &xprt_info_fops)) {
debugfs_remove_recursive(xprt->debugfs);
xprt->debugfs = NULL;
- return -ENOMEM;
}
-
- return 0;
}

void
@@ -266,14 +270,17 @@ void __exit
sunrpc_debugfs_exit(void)
{
debugfs_remove_recursive(topdir);
+ topdir = NULL;
+ rpc_clnt_dir = NULL;
+ rpc_xprt_dir = NULL;
}

-int __init
+void __init
sunrpc_debugfs_init(void)
{
topdir = debugfs_create_dir("sunrpc", NULL);
if (!topdir)
- goto out;
+ return;

rpc_clnt_dir = debugfs_create_dir("rpc_clnt", topdir);
if (!rpc_clnt_dir)
@@ -283,10 +290,9 @@ sunrpc_debugfs_init(void)
if (!rpc_xprt_dir)
goto out_remove;

- return 0;
+ return;
out_remove:
debugfs_remove_recursive(topdir);
topdir = NULL;
-out:
- return -ENOMEM;
+ rpc_clnt_dir = NULL;
}
--- a/net/sunrpc/sunrpc_syms.c
+++ b/net/sunrpc/sunrpc_syms.c
@@ -98,10 +98,7 @@ init_sunrpc(void)
if (err)
goto out4;

- err = sunrpc_debugfs_init();
- if (err)
- goto out5;
-
+ sunrpc_debugfs_init();
#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
rpc_register_sysctl();
#endif
@@ -109,8 +106,6 @@ init_sunrpc(void)
init_socket_xprt(); /* clnt sock transport */
return 0;

-out5:
- unregister_rpc_pipefs();
out4:
unregister_pernet_subsys(&sunrpc_net_ops);
out3:
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1303,7 +1303,6 @@ static void xprt_init(struct rpc_xprt *x
*/
struct rpc_xprt *xprt_create_transport(struct xprt_create *args)
{
- int err;
struct rpc_xprt *xprt;
struct xprt_class *t;

@@ -1344,11 +1343,7 @@ found:
return ERR_PTR(-ENOMEM);
}

- err = rpc_xprt_debugfs_register(xprt);
- if (err) {
- xprt_destroy(xprt);
- return ERR_PTR(err);
- }
+ rpc_xprt_debugfs_register(xprt);

dprintk("RPC: created transport %p with %u slots\n", xprt,
xprt->max_reqs);